1. Field of the Invention
The present invention relates to an optical fiber cable or duct and more particularly to such a cable or duct having an internal reinforcing member(s) for protecting the fibers from external compressive forces.
2. Discussion of Related Art
It is preferred that fiber optic cables or ducts have high compression resistance to external pressure so that the optical fibers located therein are protected from outside forces. To accomplish this objective, it is known to provide a longitudinally extending spacer member having recesses around the circumference in which the fibers are received. In U.S. Pat. No. 5,289,556, the spacer includes a crush resistant material 4 surrounding a strength member 24. The core 22 has a spoke-like configuration with the recesses being defined between each of the spokes. U.S. Pat. No. 5,920,672 discloses a similar space arrangement with a spoke-like members have a triangular-like configuration.
The problem with these prior art arrangements is that considerable material is used to form the spacer. Thus, the spacer consumes a significant amount of space inside the cable, thus reducing the amount of optical fibers that can be placed in the cable.
An object of the present invention is to provide fiber optical cable or duct having high compression resistance to external pressure while maximizing the space available for the optical fibers. The optical fiber cable or duct includes an outer jacket having a substantially tubular shape, a compression resistant core member disposed longitudinally in the outer shell and a central strength member extending through the compression resistant core member. The core member includes a plurality of Y-shaped rib members extending radially therefrom to the outer shell. A plurality of cavities are defined between the rib members for receiving the optical fibers.
According to the invention, central strength member can be made of plastic, metal, or a fiber reinforced thermoplastic or thermoset material. Further, the compression resistant core and the associated ribs can be made of either a thermoplastic or thermoset.
The unique Y-like shape of the reinforcement ribs maximizes the strength of the cable while minimizing the amount of material used for the reinforcement member. Thus, there is more space for the optical fibers. The Y shaped region can either be manufactured with the xe2x80x9cV sectionxe2x80x9d open or, alternatively, filled with a plastic material. The filled form would resemble a radial member with a fillet or radiused region where it joins the circumference.
According to another embodiment of the present invention, the optical fibers are held in buffer tubes or are arranged in a ribbon. The cable can also be used to house electrical conductors.